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How do you limit an array sub-element in MongoDB?
You can use $slice operator to limit an array. Let us create a collection with documents. Following is the query
> db.limitAnArrayDemo.insertOne(
... {
... _id: 101,
... "PlayerName": "Bob",
... "PlayerDetails": {Age:23,isStudent:true},
... "PlayerGameScores": [234,5767,58,67,78,90,1002,576,68,45,23,45,678,89,78 ]
... }
... );
{ "acknowledged" : true, "insertedId" : 101 }Following is the query to display all documents from a collection with the help of find() method
> db.limitAnArrayDemo.find().pretty();
This will produce the following output
{
"_id" : 101,
"PlayerName" : "Bob",
"PlayerDetails" : {
"Age" : 23,
"isStudent" : true
},
"PlayerGameScores" : [
234,
5767,
58,
67,
78,
90,
1002,
576,
68,
45,
23,
45,
678,
89,
78
]
}Following is the query to limit an array sub-element in MongoDB. The below query will display only 10 elements from the last
> db.limitAnArrayDemo.find({}, {PlayerName:1, PlayerDetails: 1, PlayerGameScores:{$slice: -10}}).pretty();Following is the output displaying 10 PlayerGameScores
{
"_id" : 101,
"PlayerName" : "Bob",
"PlayerDetails" : {
"Age" : 23,
"isStudent" : true
},
"PlayerGameScores" : [
90,
1002,
576,
68,
45,
23,
45,
678,
89,
78
]
}
Updated on: 30-Jul-2019
625 Views
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